Mathematical modeling of stable carbon isotope ratios in natural gases

Tang, Yongchun; Perry, J.K.; Jenden, Peter D.; Schoell, Martin

doi:10.1016/s0016-7037(00)00377-x

Cited by 395 publications

(337 citation statements)

References 28 publications

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“…In the pyrolysis experiments, d 13 C 1 initially decreased from a high value to a minimum value, and then increased with temperature and EasyR o . This reversal implies that carbon cracking changed from labile bonds (between carbon and heteroatoms) to C-C bonds (Cramer 2004), and this observation is consistent with many previous studies Lorant et al 1998;Tang et al 2000;Tian et al 2012;Xiao et al 2005;Xiong et al 2004). All pyrolysis experiments were conducted under the same pressure, excluding the possibility of varying isotopic fractionation during gas generation and expulsion under different pressures.…”

Section: Discussionsupporting

confidence: 91%

Effects of U-ore on the chemical and isotopic composition of products of hydrous pyrolysis of organic matter

Cai

Zhang

et al. 2017

Pet. Sci.

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In order to investigate the impact of U-ore on organic matter maturation and isotopic fractionation, we designed hydrous pyrolysis experiments on Type-II kerogen samples, supposing that the water and water-mineral interaction play a role. U-ore was set as the variable for comparison. Meanwhile, anhydrous pyrolysis under the same conditions was carried out as the control experiments. The determination of liquid products indicates that the presence of water and minerals obviously enhanced the yields of C 15? and the amounts of hydrocarbon and nonhydrocarbon gases. Such results may be attributed to waterorganic matter reaction in the high-temperature system, which can provide additional hydrogen and oxygen for the generation of gas and liquid products from organic matter. It is found that dD values of hydrocarbon gases generated in both hydrous pyrolysis experiments are much lower than those in anhydrous pyrolysis. What is more, dD values are lower in the hydrous pyrolysis with uranium ore. Therefore, we can infer that water-derived hydrogen played a significant role during the kerogen thermal evolution and the hydrocarbon generation in our experiments. Isotopic exchange was facilitated by the reversible equilibration between reaction intermediaries with hydrogen under hydrothermal conditions with uranium ore. Carbon isotopic fractionations of hydrocarbon gases were somehow affected by the presence of water and the uranium ore. The increased level of i-C 4 /n-C 4 ratios for gas products in hydrous pyrolysis implied the carbocation mechanism for water-kerogen reactions.

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Section: Discussionsupporting

confidence: 91%

Effects of U-ore on the chemical and isotopic composition of products of hydrous pyrolysis of organic matter

Cai

Zhang

et al. 2017

Pet. Sci.

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“…The possible explanation for this is that n-alkanes relatively depleted in D or 13 C are preferentially released from the kerogen structure in the main oil generation stage (Clayton, 1991;Tang et al, 2000). The oil expulsion causes those n-alkanes to leave the kerogen and the residual kerogen is therefore enriched in D and 13 C. At the high maturity stage, the newly formed n-alkanes are isotopicaly heavier since they are derived from residual kerogen.…”

Section: C and Dd Values Of N-alkanes In Liquid Pyrolysatesmentioning

confidence: 99%

“…10). Initial enrichment in 12 C for methane under enhanced thermal stress during pyrolysis might suggest multiple precursors for methane (Tang et al, 2000). In the oil cracking and wet gas cracking stages, methane generated from the two kerogen samples is progressively enriched in 13 C as pyrolysis temperature increases.…”

Section: C Values Of Gas Hydrocarbonsmentioning

confidence: 99%

The effect of oil expulsion or retention on further thermal degradation of kerogen at the high maturity stage: A pyrolysis study of type II kerogen from Pingliang shale, China

Jia

Wang

Liu

et al. 2014

Organic Geochemistry

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“…As shown in Figure 8a, the almost constant C 2 /C 3 ratios for Carboniferous gas indicate the secondary cracking of oils, whereas the weak sub-vertical trend for C 2 /C 3 and C 1 /C 2 in the Upper Permian and Lower Triassic gases shows great amounts of secondary cracking gas and minor contribution from primary cracking. In order to determine whether the gas in the Jiannan Gas Field was from primary kerogen cracking or secondary oil cracking, a modified model of C 2 /C 3 and δ 13 C 2 -δ 13 C 3 based on Prinzhofer's pattern (Prinzhofer and Huc, 1995) was applied, and the results from petroleum cracking experiments (Tang et al, 2000;Zhang et al, 2005) were integrated to determine the boundary of oil cracking. Although the low concentration of propane in the Upper Permian gases was not detected by chemical or carbon isotope measurement, all oil-type gas discovered in the Jiannan Gas Field falls in the area of oil and/or gas secondary cracking (Fig.…”

Section: Origin and Filling Model Of Natural Gas In Jiannan Gas Fieldmentioning

confidence: 99%

Origin and Filling Model of Natural Gas in Jiannan Gas Field, Sichuan Basin, China

Liu

Jin

et al. 2014

Energy Exploration & Exploitation

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The chemical and stable isotopic compositions of natural gases from Jiannan Gas Field, Sichuan Basin, China, were investigated to elucidate the origin of the gas and to reconstruct the reservoir filling history. The natural gases in Jiannan Gas Field are dominated by CH 4 with low amounts of non-hydrocarbon (e.g. CO 2 , H 2 S and N 2 ) components. The stable carbon isotope compositions of methane and its homologues vary widely, with an isotope trend of δ 13 C 1 ≥ δ 13 C 2 < δ 13 C 3 . Structural restoration and burial history reconstruction indicated contrasting gas-filling histories for the gas reservoirs. Natural gas in the Carboniferous reservoirs was sourced from oil and gas cracking and thermal decomposition of kerogen in the lower Silurian shale and sealed by Lower Permian shale. Natural gas in the Upper Permian reservoir was derived primarily from Upper Permian mudstone with a minor contribution from Lower Silurian shale. The sulfurbearing gas was probably sourced from Permian marine source rocks and migrated into the Lower Triassic reservoirs along unconformities and faults. Long-distance vertial migration may have caused the loss of H 2 S.

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Mathematical modeling of stable carbon isotope ratios in natural gases

Cited by 395 publications

References 28 publications

Effects of U-ore on the chemical and isotopic composition of products of hydrous pyrolysis of organic matter

Effects of U-ore on the chemical and isotopic composition of products of hydrous pyrolysis of organic matter

The effect of oil expulsion or retention on further thermal degradation of kerogen at the high maturity stage: A pyrolysis study of type II kerogen from Pingliang shale, China

Origin and Filling Model of Natural Gas in Jiannan Gas Field, Sichuan Basin, China

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